Doping-Induced Pre-Transformation to Extend Solid-Solution Regimes in Li-Ion Batteries

In many intercalation electrodes of Li-ion batteries, lithiation induces distortive structural transformations with substantial implications for stress accumulation, capacity loss, and degraded rate performance. Here, we dope a phase-transforming electrode to stabilize a structure bearing considerable similarities to the initially lithiated phase. In this “pre-transformation” approach, demonstrated based on Mo-doping of V2O5, the thermodynamic penalty associated with the phase transformation is paid in part during materials’ synthesis rather than the charge/discharge of a battery. Mo-doping alters Li–V2O5 thermodynamics to unlock extended solid-solution lithiation regimes with modulated interplanar separations. Specifically, Mo-doping reduces structural distortions during charge/discharge processes, diminishes coherency stresses, and yields a substantially modified intercalation phase diagram. Operando synchrotron X-ray diffraction and chemical lithiation results in conjunction with phase-field modeling demonstrate the promise of doping-induced structural distortions to entirely alter phase evolution and improve electrochemistry–mechanics coupling in phase-transforming cathodes.